A naphthalocyanine compound which is known as a dyestuff absorbing near infrared light is stable to light and heat, and has excellent fastness.
The dyestuff which absorbs near infrared light is known to the art, for examples, cyanines, phthalocyanines, dithionickel complexes, naphthoquinones, anthraquinones, indophenols, azo compounds and the like. The dyestuff is applicable to optical disks, compact disks, laser printers, laser reading, electrophotographic photosensitive members, infrared cut filters for semiconductor light receptors and the like. It is also proposed in Japanese Kokai Publications (unexamined) 25886/1986, 163891/1986, 233287/1987, 72594/1988, 122788/1987, 39388/1988, 252344/1985 and 16891/1986 that the dyestuff is employed in the recording layer of the optical disk.
A dyestuff for a DRAW type optical recording medium is required to have a strong absorption in the region of a laser oscillation, a high reflectance, a high stability and forming abilities of a uniform recording medium layer.
However, the cyanine dyestuff is poor in color fastness to light, and therefore a recording medium using the cyanine dyestuff is insufficient in stability. The phthalocyanine or naphthalocyanine dyestuff is poor in solubility to a polar solvent, and therefore forms an uneven recording medium layer. In order to improve the solubility of the naphthalocyanine dyestuff, there are many patent applications, such as U.S. Pat. No. 4,492,750 and Japanese Kokai Publication (unexamined) 215662/1986 in which a naphthalene ring is substituted with an alkyl group, substituted silyl group, alkoxy group, phenoxy group or aralkoxy group; Japanese Kokai Publications (unexamined) 72761/1988 and 95269/1988 in which a center metal is substituted with an alkoxy group or alkylsiloxy group. The proposed naphthalocyanine dyestuffs damage guide digs on a substrate and are still insufficient in solubility to alcohols.